From the point of view of the method the term electrically driven vehicle includes vehicles driven only in part by an electric drive, and typically such vehicles are bicycles equipped with an electric drive, and in the majority of such bicycles the rider can adjust the proportion of the human and electric powers.
The planning of optimized navigation route is especially important for electrically driven vehicles, because the operating distance that can be travelled with such vehicles is significantly shorter compared to vehicles driven by conventional fuels. Furthermore, recharging of such vehicles is also difficult because both along roads designed for normal traffic and those designed only for bicycles there are few charging station and their geographic distribution is irregular.
There are methods known for planning routes for electrically driven vehicles which take more or less into consideration the capacity of the battery and the energy required for taking the route. Such a method is described e.g. in U.S. Pat. No. 8,332,151 that uses a map database with altitude data and determined the steepness of respective sections of the planned route and calculates the expected consumption of the vehicle by summarizing the consumption of the respective road sections. That system requires the use of a separate remote server machine, and estimates with a given accuracy that when the vehicle starting with a fully charged battery has sufficient energy to take the route.
The publication JP 2011112479A deals primarily with bicycle applications and it suggests a route planning solution which takes also into account that certain driving systems are equipped with energy regeneration properties, i.e. when they are moving downward along a slope the generated energy charges the battery increasing thereby the energy stored therein. This method calculates the expected consumption based on the upward or downward steepness of the route and compares it with the capacity measured or known at the beginning of the route and plans a route along which the expected consumption will be smaller than the available capacity. The publication is silent about the details on what bases the consumption is calculated along the route however, this question has the highest significance from the point of view of the accuracy of the estimation.
It is widely know that the actual capacity of a battery depends also on the ambient temperature, the previous number of charge-discharge cycles and often from the way and extent of the load. Accordingly, it often happens that in case of a well planned consumption for a given route where the capacity of the battery was considered as sufficient, the battery will get fully discharged before the target was reached, and the vehicle cannot proceed to the target or only with the use of excess human power.
In the publication WO2013/108246 a similar method is described, in which the expected consumption is determined not only at the beginning of the route but several times when the vehicle proceeds along the route when the measured consumption of the battery is taken also into account, and when the consumption estimated till the end of the route is smaller than the available capacity, then the driver of the vehicle is warned, he is navigated to a charge station or an alternative route is suggested.
This publication is also silent concerning the question on the basis of what data and in which way the expected energy consumption is determined till the end of the route.
There is an actual need to a method and a device which can provide not only the required navigation but on the basis of a more accurate estimation it can warn the driver of the vehicle in good time in advance that the available electrical energy will prove to be too few for reaching the target. In such a case it suggests an alternative route or a different solution to the driver, which (if such exists at all) enables reaching the target with a smaller energy consumption.